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Discussion Starter #1 (Edited)
…when you buy the truck.

I've posted on this before but with $4.25 fuel out there it seems like I need to post again.

Some things improve MPG and some things kill MPG.

Like the Chinese restaurant, here’s a list. Pick and choose what you can handle.

4x4: Big killer of MPG and it forecloses some effective mods. Figure that half-ton of machinery costs you at least 2 MPG vs a 4x2 truck.

Automatic transmission: Another big MPG-killer. It is good for 2 MPG loss vs a six-speed

Dually: It will cost you 1 MPG over a SRW

Crew Cab: It will cost you 0.75 MPG vs a regular cab

Club Cab: It will cost you 0.5 MPG vs a regular cab

Big tires: Anything over 235-85 or 265-75 will hurt. Figure 285s will cost you 1 MPG 305s will cost yet another 1 MPG (this applies to used trucks or dealer-modded trucks only)

Lift: It will cost you 2 MPG vs stock height (this applies to used trucks or dealer-modded trucks only)

Gearing: Very strong effect on MPG
3.55s will get 1 MPG better than 3.73s (all else equal) I understand 3.55s are now standard for 6.4s.
3.73s will get 1 MPG better than 4.10s
My 3.08s (not widely available) improved my economy by 3 MPG over the stock 3.73s

The 6.0 and 6.4 are somewhat less efficient due to EGR and the filter thingy but I would expect a RC 4x2 six-speed SRW with stock tires and the stock 3.73 gears to get 19-20 MPG if driven normally.

All the stuff above adds up.

A CC 4x4 automatic dually with 305s and a lift and 4.10 gears should expect about 9-10 MPG.

There is some variability in this so YMMV.

To add insult to injury, the higher MPG truck will probably set you back $10-12,000 less up front. Even with my exotic drivetrain and aero mods, my truck may be one of the ten lowest-cost trucks in the DieselStop community.

All these numbers square with my experience and what I have found out talking to literally hundreds of guys plus design engineers.

Its your money. You know what you want/need. Get what you will but those numbers outline the unmodded MPG you can expect. The specification sheet is a powerful tool for good MPG from the git-go.
 

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Dave,

All good info, but this forum is pretty much dead. Might post it up in the 6.4 / 08 section, or general diesel.

OMC
 

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Thank you, Dave, for this extremely valuable information.

I have the 4X4, automatic transmission, crew cab, duallies, 4.10, standard tires, no lift.

If I am adding it up right, I should get 19-20 minus 2 for 4X4 minus 2 for automatic minus 1 for duallies minus 0.75 for crew cab minus 1 for 4.10 equals 12.25 to 13.25 mpg.

What can I do? Should I mod it to run on wvo? Do I have any other options?
 

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Thank you, Dave, for this extremely valuable information.

I have the 4X4, automatic transmission, crew cab, duallies, 4.10, standard tires, no lift.

If I am adding it up right, I should get 19-20 minus 2 for 4X4 minus 2 for automatic minus 1 for duallies minus 0.75 for crew cab minus 1 for 4.10 equals 12.25 to 13.25 mpg.

What can I do? Should I mod it to run on wvo? Do I have any other options?
WVO won't give you any better milage, and can cause you problems with your injectors. You'll save money if you get the oil for free, but you'll spend time getting it properly prepped for use and money on the mods for using it.

You'd be better off building a biodiesel processor and using that, but the time involved is still there.

Now comes the hard question - do you really need the truck you have? Is it a work truck, a daily driver or an RV tug? Do you really need the turbo diesel, or will a gasser do the job. These are very hard questions for us all, but if fuel economy is a concern, they are valid, and need honest answers.

If you do allot of highway, one of the best things you could do is add a tapered cap to the back. If you don't drive highway, you just gotta suck it up and drive with an egg between your foot & the excelarator, and remove the brake pedal.

OMC
 

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Discussion Starter #5
Good point OMCUSNR. I'll post in that forum.

Don, PM me. I'll have questions.
 

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What is it about the automatic that sucks the energy? Can anything be done about it? I'm guessing the sloppy TC is a big contributor to this, could an aftermarket one minimize the losses there?
Also in regards to gearing, what is the difference between 3.73 gears with 265 tires and 4.1 gears with 285 tires. Is it just the unsprung weight and the tread width that are the contributing factors there?
In regards to gearing, would it be safe to say that 3.08 gears would be ideal and that a 'underdrive' transmission would be the way to go for heavy towing? I realize this is prohibitively expensive changing both gears and adding an aux trans.
No way to lower the front end of a 4x4 is there?
And last, how's that fastback coming?
 

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Ok what would the approximate mileage be on this truck??

Crew Cab, Short Bed, F-250, 4x4, 7.3L, Auto, 6" lift, 37x13.50x20 Pro-Comp XATs, 4.30 gears & Lockers...Oh and a heavy Egg Smashing Foot.......:lol:


Just Curious.......:thumbsup:
 

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What is it about the automatic that sucks the energy? Can anything be done about it? I'm guessing the sloppy TC is a big contributor to this, could an aftermarket one minimize the losses there?
Also in regards to gearing, what is the difference between 3.73 gears with 265 tires and 4.1 gears with 285 tires. Is it just the unsprung weight and the tread width that are the contributing factors there?
In regards to gearing, would it be safe to say that 3.08 gears would be ideal and that a 'underdrive' transmission would be the way to go for heavy towing? I realize this is prohibitively expensive changing both gears and adding an aux trans.
No way to lower the front end of a 4x4 is there?
And last, how's that fastback coming?
Blackout,

The auto tranny, has slippage in the lower gears (tc unlocked), hence it sucks up fuel. once the tc is locked up and on overdrive, mileage improves.
Manual tranny will give you slightly better mileage over the auto, but being stuck in stop and go traffic, the manual tranny in not for me.

I spent too many years w/ "clutch leg" dealing w/ the manual tranny. Auto is the only thing I will drive now. Also I don't miss doing the constant clutch jobs that I had to perform on the trucks that I own.

Auto trannys have come a long way over the years, especially the last couple of years, auto trannys are coming thru w/ more gearing in them.

butchcassidy1
 

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On ordering a truck, the best approach I found is to DEFINE YOUR NEEDS. Do you really need a truck or could you get by w/ a fuel sipping car. I used to tow a 26' trailer w/ the current truck. Now I occasionally haul a light weight camper and tow a m/c trailer.

If I were looking for a new vehicle, I would keep the current truck and get a small daily driver. I don't need a big truck to impress others - much too expensive.

A lot of building trade people that I know are doing the above -going to bid on a job using a small 4 cylinder car. When they get the job, the truck gets loaded up w/ tools, supplies, poeple and off to the job site.

The use of the big truck is being limited in use due to the ever increasing price of fuel. Many, people who use their truck for work are trying to get by w/ smaller more fuel efficient cars - some can do this, others can not.

Hopefully, all of us will see a lowering of fuel prices - it really will help the economy out.

butchcassidy1
 

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Ok Dave,
I bought a 99 F350 crew cab 4x4 with 101K on it. Now that I've seen your thougths on MPG, I don't "think something must be wrong" However, there are some things, i.e. air intake, exhaust, and perhaps even a computer chip that promise to improve mileage. Any thoughts on those three mods?
On a seperate note, I must say I like what you did with your truck. My dad had a 3/4 Chevy with a 6.2 and put a 3.23 rear end in it with a 25% behind the tranny overdrive that made a final drive of 2.4something. Thing took forever to get to 70 MPH but boy when it got there it did it at 29 MPG.
 

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victorng -

Welcome to TheDieselStop.

You dug up an old thead from June, 2008. Which would be fine in most forums. But as noted early in this thread, this forum was orphaned by the new '08-up Ordering Info forum several months before that. So "nobody" monitors this forum now. I glance at it only once a week or so, and this is the first time I noticed your post. If you want an answer, you might want to post your questions is an active forum on TheDieselStop. :)

Smokey
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